builtin/checkout.c

   1 #include "cache.h"
   2 #include "builtin.h"
   3 #include "parse-options.h"
   4 #include "refs.h"
   5 #include "commit.h"
   6 #include "tree.h"
   7 #include "tree-walk.h"
   8 #include "cache-tree.h"
   9 #include "unpack-trees.h"
  10 #include "dir.h"
  11 #include "run-command.h"
  12 #include "merge-recursive.h"
  13 #include "branch.h"
  14 #include "diff.h"
  15 #include "revision.h"
  16 #include "remote.h"
  17 #include "blob.h"
  18 #include "xdiff-interface.h"
  19 #include "ll-merge.h"
  20 #include "resolve-undo.h"
  21 #include "submodule.h"
  22 #include "argv-array.h"
  23
  24 static const char * const checkout_usage[] = {
  25         "git checkout [options] <branch>",
  26         "git checkout [options] [<branch>] -- <file>...",
  27         NULL,
  28 };
  29
  30 struct checkout_opts {
  31         int quiet;
  32         int merge;
  33         int force;
  34         int force_detach;
  35         int writeout_stage;
  36         int writeout_error;
  37
  38         /* not set by parse_options */
  39         int branch_exists;
  40
  41         const char *new_branch;
  42         const char *new_branch_force;
  43         const char *new_orphan_branch;
  44         int new_branch_log;
  45         enum branch_track track;
  46         struct diff_options diff_options;
  47 };
  48
  49 static int post_checkout_hook(struct commit *old, struct commit *new,
  50                               int changed)
  51 {
  52         return run_hook(NULL, "post-checkout",
  53                         sha1_to_hex(old ? old->object.sha1 : null_sha1),
  54                         sha1_to_hex(new ? new->object.sha1 : null_sha1),
  55                         changed ? "1" : "0", NULL);
  56         /* "new" can be NULL when checking out from the index before
  57            a commit exists. */
  58
  59 }
  60
  61 static int update_some(const unsigned char *sha1, const char *base, int baselen,
  62                 const char *pathname, unsigned mode, int stage, void *context)
  63 {
  64         int len;
  65         struct cache_entry *ce;
  66
  67         if (S_ISDIR(mode))
  68                 return READ_TREE_RECURSIVE;
  69
  70         len = baselen + strlen(pathname);
  71         ce = xcalloc(1, cache_entry_size(len));
  72         hashcpy(ce->sha1, sha1);
  73         memcpy(ce->name, base, baselen);
  74         memcpy(ce->name + baselen, pathname, len - baselen);
  75         ce->ce_flags = create_ce_flags(len, 0);
  76         ce->ce_mode = create_ce_mode(mode);
  77         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
  78         return 0;
  79 }
  80
  81 static int read_tree_some(struct tree *tree, const char **pathspec)
  82 {
  83         struct pathspec ps;
  84         init_pathspec(&ps, pathspec);
  85         read_tree_recursive(tree, "", 0, 0, &ps, update_some, NULL);
  86         free_pathspec(&ps);
  87
  88         /* update the index with the given tree's info
  89          * for all args, expanding wildcards, and exit
  90          * with any non-zero return code.
  91          */
  92         return 0;
  93 }
  94
  95 static int skip_same_name(struct cache_entry *ce, int pos)
  96 {
  97         while (++pos < active_nr &&
  98                !strcmp(active_cache[pos]->name, ce->name))
  99                 ; /* skip */
 100         return pos;
 101 }
 102
 103 static int check_stage(int stage, struct cache_entry *ce, int pos)
 104 {
 105         while (pos < active_nr &&
 106                !strcmp(active_cache[pos]->name, ce->name)) {
 107                 if (ce_stage(active_cache[pos]) == stage)
 108                         return 0;
 109                 pos++;
 110         }
 111         if (stage == 2)
 112                 return error(_("path '%s' does not have our version"), ce->name);
 113         else
 114                 return error(_("path '%s' does not have their version"), ce->name);
 115 }
 116
 117 static int check_all_stages(struct cache_entry *ce, int pos)
 118 {
 119         if (ce_stage(ce) != 1 ||
 120             active_nr <= pos + 2 ||
 121             strcmp(active_cache[pos+1]->name, ce->name) ||
 122             ce_stage(active_cache[pos+1]) != 2 ||
 123             strcmp(active_cache[pos+2]->name, ce->name) ||
 124             ce_stage(active_cache[pos+2]) != 3)
 125                 return error(_("path '%s' does not have all three versions"),
 126                              ce->name);
 127         return 0;
 128 }
 129
 130 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
 131                           struct checkout *state)
 132 {
 133         while (pos < active_nr &&
 134                !strcmp(active_cache[pos]->name, ce->name)) {
 135                 if (ce_stage(active_cache[pos]) == stage)
 136                         return checkout_entry(active_cache[pos], state, NULL);
 137                 pos++;
 138         }
 139         if (stage == 2)
 140                 return error(_("path '%s' does not have our version"), ce->name);
 141         else
 142                 return error(_("path '%s' does not have their version"), ce->name);
 143 }
 144
 145 static int checkout_merged(int pos, struct checkout *state)
 146 {
 147         struct cache_entry *ce = active_cache[pos];
 148         const char *path = ce->name;
 149         mmfile_t ancestor, ours, theirs;
 150         int status;
 151         unsigned char sha1[20];
 152         mmbuffer_t result_buf;
 153
 154         if (ce_stage(ce) != 1 ||
 155             active_nr <= pos + 2 ||
 156             strcmp(active_cache[pos+1]->name, path) ||
 157             ce_stage(active_cache[pos+1]) != 2 ||
 158             strcmp(active_cache[pos+2]->name, path) ||
 159             ce_stage(active_cache[pos+2]) != 3)
 160                 return error(_("path '%s' does not have all 3 versions"), path);
 161
 162         read_mmblob(&ancestor, active_cache[pos]->sha1);
 163         read_mmblob(&ours, active_cache[pos+1]->sha1);
 164         read_mmblob(&theirs, active_cache[pos+2]->sha1);
 165
 166         /*
 167          * NEEDSWORK: re-create conflicts from merges with
 168          * merge.renormalize set, too
 169          */
 170         status = ll_merge(&result_buf, path, &ancestor, "base",
 171                           &ours, "ours", &theirs, "theirs", NULL);
 172         free(ancestor.ptr);
 173         free(ours.ptr);
 174         free(theirs.ptr);
 175         if (status < 0 || !result_buf.ptr) {
 176                 free(result_buf.ptr);
 177                 return error(_("path '%s': cannot merge"), path);
 178         }
 179
 180         /*
 181          * NEEDSWORK:
 182          * There is absolutely no reason to write this as a blob object
 183          * and create a phony cache entry just to leak.  This hack is
 184          * primarily to get to the write_entry() machinery that massages
 185          * the contents to work-tree format and writes out which only
 186          * allows it for a cache entry.  The code in write_entry() needs
 187          * to be refactored to allow us to feed a <buffer, size, mode>
 188          * instead of a cache entry.  Such a refactoring would help
 189          * merge_recursive as well (it also writes the merge result to the
 190          * object database even when it may contain conflicts).
 191          */
 192         if (write_sha1_file(result_buf.ptr, result_buf.size,
 193                             blob_type, sha1))
 194                 die(_("Unable to add merge result for '%s'"), path);
 195         ce = make_cache_entry(create_ce_mode(active_cache[pos+1]->ce_mode),
 196                               sha1,
 197                               path, 2, 0);
 198         if (!ce)
 199                 die(_("make_cache_entry failed for path '%s'"), path);
 200         status = checkout_entry(ce, state, NULL);
 201         return status;
 202 }
 203
 204 static int checkout_paths(struct tree *source_tree, const char **pathspec,
 205                           const char *prefix, struct checkout_opts *opts)
 206 {
 207         int pos;
 208         struct checkout state;
 209         static char *ps_matched;
 210         unsigned char rev[20];
 211         int flag;
 212         struct commit *head;
 213         int errs = 0;
 214         int stage = opts->writeout_stage;
 215         int merge = opts->merge;
 216         int newfd;
 217         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 218
 219         newfd = hold_locked_index(lock_file, 1);
 220         if (read_cache_preload(pathspec) < 0)
 221                 return error(_("corrupt index file"));
 222
 223         if (source_tree)
 224                 read_tree_some(source_tree, pathspec);
 225
 226         for (pos = 0; pathspec[pos]; pos++)
 227                 ;
 228         ps_matched = xcalloc(1, pos);
 229
 230         for (pos = 0; pos < active_nr; pos++) {
 231                 struct cache_entry *ce = active_cache[pos];
 232                 match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
 233         }
 234
 235         if (report_path_error(ps_matched, pathspec, prefix))
 236                 return 1;
 237
 238         /* "checkout -m path" to recreate conflicted state */
 239         if (opts->merge)
 240                 unmerge_cache(pathspec);
 241
 242         /* Any unmerged paths? */
 243         for (pos = 0; pos < active_nr; pos++) {
 244                 struct cache_entry *ce = active_cache[pos];
 245                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 246                         if (!ce_stage(ce))
 247                                 continue;
 248                         if (opts->force) {
 249                                 warning(_("path '%s' is unmerged"), ce->name);
 250                         } else if (stage) {
 251                                 errs |= check_stage(stage, ce, pos);
 252                         } else if (opts->merge) {
 253                                 errs |= check_all_stages(ce, pos);
 254                         } else {
 255                                 errs = 1;
 256                                 error(_("path '%s' is unmerged"), ce->name);
 257                         }
 258                         pos = skip_same_name(ce, pos) - 1;
 259                 }
 260         }
 261         if (errs)
 262                 return 1;
 263
 264         /* Now we are committed to check them out */
 265         memset(&state, 0, sizeof(state));
 266         state.force = 1;
 267         state.refresh_cache = 1;
 268         for (pos = 0; pos < active_nr; pos++) {
 269                 struct cache_entry *ce = active_cache[pos];
 270                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 271                         if (!ce_stage(ce)) {
 272                                 errs |= checkout_entry(ce, &state, NULL);
 273                                 continue;
 274                         }
 275                         if (stage)
 276                                 errs |= checkout_stage(stage, ce, pos, &state);
 277                         else if (merge)
 278                                 errs |= checkout_merged(pos, &state);
 279                         pos = skip_same_name(ce, pos) - 1;
 280                 }
 281         }
 282
 283         if (write_cache(newfd, active_cache, active_nr) ||
 284             commit_locked_index(lock_file))
 285                 die(_("unable to write new index file"));
 286
 287         resolve_ref("HEAD", rev, 0, &flag);
 288         head = lookup_commit_reference_gently(rev, 1);
 289
 290         errs |= post_checkout_hook(head, head, 0);
 291         return errs;
 292 }
 293
 294 static void show_local_changes(struct object *head, struct diff_options *opts)
 295 {
 296         struct rev_info rev;
 297         /* I think we want full paths, even if we're in a subdirectory. */
 298         init_revisions(&rev, NULL);
 299         rev.diffopt.flags = opts->flags;
 300         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 301         if (diff_setup_done(&rev.diffopt) < 0)
 302                 die(_("diff_setup_done failed"));
 303         add_pending_object(&rev, head, NULL);
 304         run_diff_index(&rev, 0);
 305 }
 306
 307 static void describe_detached_head(const char *msg, struct commit *commit)
 308 {
 309         struct strbuf sb = STRBUF_INIT;
 310         parse_commit(commit);
 311         pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 312         fprintf(stderr, "%s %s... %s\n", msg,
 313                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 314         strbuf_release(&sb);
 315 }
 316
 317 static int reset_tree(struct tree *tree, struct checkout_opts *o, int worktree)
 318 {
 319         struct unpack_trees_options opts;
 320         struct tree_desc tree_desc;
 321
 322         memset(&opts, 0, sizeof(opts));
 323         opts.head_idx = -1;
 324         opts.update = worktree;
 325         opts.skip_unmerged = !worktree;
 326         opts.reset = 1;
 327         opts.merge = 1;
 328         opts.fn = oneway_merge;
 329         opts.verbose_update = !o->quiet;
 330         opts.src_index = &the_index;
 331         opts.dst_index = &the_index;
 332         parse_tree(tree);
 333         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 334         switch (unpack_trees(1, &tree_desc, &opts)) {
 335         case -2:
 336                 o->writeout_error = 1;
 337                 /*
 338                  * We return 0 nevertheless, as the index is all right
 339                  * and more importantly we have made best efforts to
 340                  * update paths in the work tree, and we cannot revert
 341                  * them.
 342                  */
 343         case 0:
 344                 return 0;
 345         default:
 346                 return 128;
 347         }
 348 }
 349
 350 struct branch_info {
 351         const char *name; /* The short name used */
 352         const char *path; /* The full name of a real branch */
 353         struct commit *commit; /* The named commit */
 354 };
 355
 356 static void setup_branch_path(struct branch_info *branch)
 357 {
 358         struct strbuf buf = STRBUF_INIT;
 359
 360         strbuf_branchname(&buf, branch->name);
 361         if (strcmp(buf.buf, branch->name))
 362                 branch->name = xstrdup(buf.buf);
 363         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 364         branch->path = strbuf_detach(&buf, NULL);
 365 }
 366
 367 static int merge_working_tree(struct checkout_opts *opts,
 368                               struct branch_info *old, struct branch_info *new)
 369 {
 370         int ret;
 371         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 372         int newfd = hold_locked_index(lock_file, 1);
 373
 374         if (read_cache_preload(NULL) < 0)
 375                 return error(_("corrupt index file"));
 376
 377         resolve_undo_clear();
 378         if (opts->force) {
 379                 ret = reset_tree(new->commit->tree, opts, 1);
 380                 if (ret)
 381                         return ret;
 382         } else {
 383                 struct tree_desc trees[2];
 384                 struct tree *tree;
 385                 struct unpack_trees_options topts;
 386
 387                 memset(&topts, 0, sizeof(topts));
 388                 topts.head_idx = -1;
 389                 topts.src_index = &the_index;
 390                 topts.dst_index = &the_index;
 391
 392                 setup_unpack_trees_porcelain(&topts, "checkout");
 393
 394                 refresh_cache(REFRESH_QUIET);
 395
 396                 if (unmerged_cache()) {
 397                         error(_("you need to resolve your current index first"));
 398                         return 1;
 399                 }
 400
 401                 /* 2-way merge to the new branch */
 402                 topts.initial_checkout = is_cache_unborn();
 403                 topts.update = 1;
 404                 topts.merge = 1;
 405                 topts.gently = opts->merge && old->commit;
 406                 topts.verbose_update = !opts->quiet;
 407                 topts.fn = twoway_merge;
 408                 topts.dir = xcalloc(1, sizeof(*topts.dir));
 409                 topts.dir->flags |= DIR_SHOW_IGNORED;
 410                 topts.dir->exclude_per_dir = ".gitignore";
 411                 tree = parse_tree_indirect(old->commit ?
 412                                            old->commit->object.sha1 :
 413                                            EMPTY_TREE_SHA1_BIN);
 414                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 415                 tree = parse_tree_indirect(new->commit->object.sha1);
 416                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 417
 418                 ret = unpack_trees(2, trees, &topts);
 419                 if (ret == -1) {
 420                         /*
 421                          * Unpack couldn't do a trivial merge; either
 422                          * give up or do a real merge, depending on
 423                          * whether the merge flag was used.
 424                          */
 425                         struct tree *result;
 426                         struct tree *work;
 427                         struct merge_options o;
 428                         if (!opts->merge)
 429                                 return 1;
 430
 431                         /*
 432                          * Without old->commit, the below is the same as
 433                          * the two-tree unpack we already tried and failed.
 434                          */
 435                         if (!old->commit)
 436                                 return 1;
 437
 438                         /* Do more real merge */
 439
 440                         /*
 441                          * We update the index fully, then write the
 442                          * tree from the index, then merge the new
 443                          * branch with the current tree, with the old
 444                          * branch as the base. Then we reset the index
 445                          * (but not the working tree) to the new
 446                          * branch, leaving the working tree as the
 447                          * merged version, but skipping unmerged
 448                          * entries in the index.
 449                          */
 450
 451                         add_files_to_cache(NULL, NULL, 0);
 452                         /*
 453                          * NEEDSWORK: carrying over local changes
 454                          * when branches have different end-of-line
 455                          * normalization (or clean+smudge rules) is
 456                          * a pain; plumb in an option to set
 457                          * o.renormalize?
 458                          */
 459                         init_merge_options(&o);
 460                         o.verbosity = 0;
 461                         work = write_tree_from_memory(&o);
 462
 463                         ret = reset_tree(new->commit->tree, opts, 1);
 464                         if (ret)
 465                                 return ret;
 466                         o.ancestor = old->name;
 467                         o.branch1 = new->name;
 468                         o.branch2 = "local";
 469                         merge_trees(&o, new->commit->tree, work,
 470                                 old->commit->tree, &result);
 471                         ret = reset_tree(new->commit->tree, opts, 0);
 472                         if (ret)
 473                                 return ret;
 474                 }
 475         }
 476
 477         if (write_cache(newfd, active_cache, active_nr) ||
 478             commit_locked_index(lock_file))
 479                 die(_("unable to write new index file"));
 480
 481         if (!opts->force && !opts->quiet)
 482                 show_local_changes(&new->commit->object, &opts->diff_options);
 483
 484         return 0;
 485 }
 486
 487 static void report_tracking(struct branch_info *new)
 488 {
 489         struct strbuf sb = STRBUF_INIT;
 490         struct branch *branch = branch_get(new->name);
 491
 492         if (!format_tracking_info(branch, &sb))
 493                 return;
 494         fputs(sb.buf, stdout);
 495         strbuf_release(&sb);
 496 }
 497
 498 static void detach_advice(const char *old_path, const char *new_name)
 499 {
 500         const char fmt[] =
 501         "Note: checking out '%s'.\n\n"
 502         "You are in 'detached HEAD' state. You can look around, make experimental\n"
 503         "changes and commit them, and you can discard any commits you make in this\n"
 504         "state without impacting any branches by performing another checkout.\n\n"
 505         "If you want to create a new branch to retain commits you create, you may\n"
 506         "do so (now or later) by using -b with the checkout command again. Example:\n\n"
 507         "  git checkout -b new_branch_name\n\n";
 508
 509         fprintf(stderr, fmt, new_name);
 510 }
 511
 512 static void update_refs_for_switch(struct checkout_opts *opts,
 513                                    struct branch_info *old,
 514                                    struct branch_info *new)
 515 {
 516         struct strbuf msg = STRBUF_INIT;
 517         const char *old_desc;
 518         if (opts->new_branch) {
 519                 if (opts->new_orphan_branch) {
 520                         if (opts->new_branch_log && !log_all_ref_updates) {
 521                                 int temp;
 522                                 char log_file[PATH_MAX];
 523                                 char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 524
 525                                 temp = log_all_ref_updates;
 526                                 log_all_ref_updates = 1;
 527                                 if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
 528                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
 529                                             opts->new_orphan_branch);
 530                                         log_all_ref_updates = temp;
 531                                         return;
 532                                 }
 533                                 log_all_ref_updates = temp;
 534                         }
 535                 }
 536                 else
 537                         create_branch(old->name, opts->new_branch, new->name,
 538                                       opts->new_branch_force ? 1 : 0,
 539                                       opts->new_branch_log, opts->track);
 540                 new->name = opts->new_branch;
 541                 setup_branch_path(new);
 542         }
 543
 544         old_desc = old->name;
 545         if (!old_desc && old->commit)
 546                 old_desc = sha1_to_hex(old->commit->object.sha1);
 547         strbuf_addf(&msg, "checkout: moving from %s to %s",
 548                     old_desc ? old_desc : "(invalid)", new->name);
 549
 550         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 551                 /* Nothing to do. */
 552         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 553                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 554                            REF_NODEREF, DIE_ON_ERR);
 555                 if (!opts->quiet) {
 556                         if (old->path && advice_detached_head)
 557                                 detach_advice(old->path, new->name);
 558                         describe_detached_head(_("HEAD is now at"), new->commit);
 559                 }
 560         } else if (new->path) { /* Switch branches. */
 561                 create_symref("HEAD", new->path, msg.buf);
 562                 if (!opts->quiet) {
 563                         if (old->path && !strcmp(new->path, old->path)) {
 564                                 fprintf(stderr, _("Already on '%s'\n"),
 565                                         new->name);
 566                         } else if (opts->new_branch) {
 567                                 if (opts->branch_exists)
 568                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 569                                 else
 570                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 571                         } else {
 572                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 573                                         new->name);
 574                         }
 575                 }
 576                 if (old->path && old->name) {
 577                         char log_file[PATH_MAX], ref_file[PATH_MAX];
 578
 579                         git_snpath(log_file, sizeof(log_file), "logs/%s", old->path);
 580                         git_snpath(ref_file, sizeof(ref_file), "%s", old->path);
 581                         if (!file_exists(ref_file) && file_exists(log_file))
 582                                 remove_path(log_file);
 583                 }
 584         }
 585         remove_branch_state();
 586         strbuf_release(&msg);
 587         if (!opts->quiet &&
 588             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 589                 report_tracking(new);
 590 }
 591
 592 static int add_one_ref_to_rev_list_arg(const char *refname,
 593                                        const unsigned char *sha1,
 594                                        int flags,
 595                                        void *cb_data)
 596 {
 597         argv_array_push(cb_data, refname);
 598         return 0;
 599 }
 600
 601 static int clear_commit_marks_from_one_ref(const char *refname,
 602                                       const unsigned char *sha1,
 603                                       int flags,
 604                                       void *cb_data)
 605 {
 606         struct commit *commit = lookup_commit_reference_gently(sha1, 1);
 607         if (commit)
 608                 clear_commit_marks(commit, -1);
 609         return 0;
 610 }
 611
 612 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 613 {
 614         parse_commit(commit);
 615         strbuf_addstr(sb, "  ");
 616         strbuf_addstr(sb,
 617                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 618         strbuf_addch(sb, ' ');
 619         pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 620         strbuf_addch(sb, '\n');
 621 }
 622
 623 #define ORPHAN_CUTOFF 4
 624 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 625 {
 626         struct commit *c, *last = NULL;
 627         struct strbuf sb = STRBUF_INIT;
 628         int lost = 0;
 629         while ((c = get_revision(revs)) != NULL) {
 630                 if (lost < ORPHAN_CUTOFF)
 631                         describe_one_orphan(&sb, c);
 632                 last = c;
 633                 lost++;
 634         }
 635         if (ORPHAN_CUTOFF < lost) {
 636                 int more = lost - ORPHAN_CUTOFF;
 637                 if (more == 1)
 638                         describe_one_orphan(&sb, last);
 639                 else
 640                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 641         }
 642
 643         fprintf(stderr,
 644                 Q_(
 645                 /* The singular version */
 646                 "Warning: you are leaving %d commit behind, "
 647                 "not connected to\n"
 648                 "any of your branches:\n\n"
 649                 "%s\n",
 650                 /* The plural version */
 651                 "Warning: you are leaving %d commits behind, "
 652                 "not connected to\n"
 653                 "any of your branches:\n\n"
 654                 "%s\n",
 655                 /* Give ngettext() the count */
 656                 lost),
 657                 lost,
 658                 sb.buf);
 659         strbuf_release(&sb);
 660
 661         if (advice_detached_head)
 662                 fprintf(stderr,
 663                         _(
 664                         "If you want to keep them by creating a new branch, "
 665                         "this may be a good time\nto do so with:\n\n"
 666                         " git branch new_branch_name %s\n\n"),
 667                         sha1_to_hex(commit->object.sha1));
 668 }
 669
 670 /*
 671  * We are about to leave commit that was at the tip of a detached
 672  * HEAD.  If it is not reachable from any ref, this is the last chance
 673  * for the user to do so without resorting to reflog.
 674  */
 675 static void orphaned_commit_warning(struct commit *commit)
 676 {
 677         struct argv_array args = ARGV_ARRAY_INIT;
 678         struct rev_info revs;
 679
 680         argv_array_push(&args, "(internal)");
 681         argv_array_push(&args, sha1_to_hex(commit->object.sha1));
 682         argv_array_push(&args, "--not");
 683         for_each_ref(add_one_ref_to_rev_list_arg, &args);
 684         argv_array_push(&args, "--");
 685
 686         init_revisions(&revs, NULL);
 687         if (setup_revisions(args.argc - 1, args.argv, &revs, NULL) != 1)
 688                 die(_("internal error: only -- alone should have been left"));
 689         if (prepare_revision_walk(&revs))
 690                 die(_("internal error in revision walk"));
 691         if (!(commit->object.flags & UNINTERESTING))
 692                 suggest_reattach(commit, &revs);
 693         else
 694                 describe_detached_head(_("Previous HEAD position was"), commit);
 695
 696         argv_array_clear(&args);
 697         clear_commit_marks(commit, -1);
 698         for_each_ref(clear_commit_marks_from_one_ref, NULL);
 699 }
 700
 701 static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 702 {
 703         int ret = 0;
 704         struct branch_info old;
 705         unsigned char rev[20];
 706         int flag;
 707         memset(&old, 0, sizeof(old));
 708         old.path = xstrdup(resolve_ref("HEAD", rev, 0, &flag));
 709         old.commit = lookup_commit_reference_gently(rev, 1);
 710         if (!(flag & REF_ISSYMREF)) {
 711                 free((char *)old.path);
 712                 old.path = NULL;
 713         }
 714
 715         if (old.path && !prefixcmp(old.path, "refs/heads/"))
 716                 old.name = old.path + strlen("refs/heads/");
 717
 718         if (!new->name) {
 719                 new->name = "HEAD";
 720                 new->commit = old.commit;
 721                 if (!new->commit)
 722                         die(_("You are on a branch yet to be born"));
 723                 parse_commit(new->commit);
 724         }
 725
 726         ret = merge_working_tree(opts, &old, new);
 727         if (ret)
 728                 return ret;
 729
 730         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
 731                 orphaned_commit_warning(old.commit);
 732
 733         update_refs_for_switch(opts, &old, new);
 734
 735         ret = post_checkout_hook(old.commit, new->commit, 1);
 736         free((char *)old.path);
 737         return ret || opts->writeout_error;
 738 }
 739
 740 static int git_checkout_config(const char *var, const char *value, void *cb)
 741 {
 742         if (!strcmp(var, "diff.ignoresubmodules")) {
 743                 struct checkout_opts *opts = cb;
 744                 handle_ignore_submodules_arg(&opts->diff_options, value);
 745                 return 0;
 746         }
 747
 748         if (!prefixcmp(var, "submodule."))
 749                 return parse_submodule_config_option(var, value);
 750
 751         return git_xmerge_config(var, value, NULL);
 752 }
 753
 754 static int interactive_checkout(const char *revision, const char **pathspec,
 755                                 struct checkout_opts *opts)
 756 {
 757         return run_add_interactive(revision, "--patch=checkout", pathspec);
 758 }
 759
 760 struct tracking_name_data {
 761         const char *name;
 762         char *remote;
 763         int unique;
 764 };
 765
 766 static int check_tracking_name(const char *refname, const unsigned char *sha1,
 767                                int flags, void *cb_data)
 768 {
 769         struct tracking_name_data *cb = cb_data;
 770         const char *slash;
 771
 772         if (prefixcmp(refname, "refs/remotes/"))
 773                 return 0;
 774         slash = strchr(refname + 13, '/');
 775         if (!slash || strcmp(slash + 1, cb->name))
 776                 return 0;
 777         if (cb->remote) {
 778                 cb->unique = 0;
 779                 return 0;
 780         }
 781         cb->remote = xstrdup(refname);
 782         return 0;
 783 }
 784
 785 static const char *unique_tracking_name(const char *name)
 786 {
 787         struct tracking_name_data cb_data = { NULL, NULL, 1 };
 788         cb_data.name = name;
 789         for_each_ref(check_tracking_name, &cb_data);
 790         if (cb_data.unique)
 791                 return cb_data.remote;
 792         free(cb_data.remote);
 793         return NULL;
 794 }
 795
 796 static int parse_branchname_arg(int argc, const char **argv,
 797                                 int dwim_new_local_branch_ok,
 798                                 struct branch_info *new,
 799                                 struct tree **source_tree,
 800                                 unsigned char rev[20],
 801                                 const char **new_branch)
 802 {
 803         int argcount = 0;
 804         unsigned char branch_rev[20];
 805         const char *arg;
 806         int has_dash_dash;
 807
 808         /*
 809          * case 1: git checkout <ref> -- [<paths>]
 810          *
 811          *   <ref> must be a valid tree, everything after the '--' must be
 812          *   a path.
 813          *
 814          * case 2: git checkout -- [<paths>]
 815          *
 816          *   everything after the '--' must be paths.
 817          *
 818          * case 3: git checkout <something> [<paths>]
 819          *
 820          *   With no paths, if <something> is a commit, that is to
 821          *   switch to the branch or detach HEAD at it.  As a special case,
 822          *   if <something> is A...B (missing A or B means HEAD but you can
 823          *   omit at most one side), and if there is a unique merge base
 824          *   between A and B, A...B names that merge base.
 825          *
 826          *   With no paths, if <something> is _not_ a commit, no -t nor -b
 827          *   was given, and there is a tracking branch whose name is
 828          *   <something> in one and only one remote, then this is a short-hand
 829          *   to fork local <something> from that remote-tracking branch.
 830          *
 831          *   Otherwise <something> shall not be ambiguous.
 832          *   - If it's *only* a reference, treat it like case (1).
 833          *   - If it's only a path, treat it like case (2).
 834          *   - else: fail.
 835          *
 836          */
 837         if (!argc)
 838                 return 0;
 839
 840         if (!strcmp(argv[0], "--"))     /* case (2) */
 841                 return 1;
 842
 843         arg = argv[0];
 844         has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
 845
 846         if (!strcmp(arg, "-"))
 847                 arg = "@{-1}";
 848
 849         if (get_sha1_mb(arg, rev)) {
 850                 if (has_dash_dash)          /* case (1) */
 851                         die(_("invalid reference: %s"), arg);
 852                 if (dwim_new_local_branch_ok &&
 853                     !check_filename(NULL, arg) &&
 854                     argc == 1) {
 855                         const char *remote = unique_tracking_name(arg);
 856                         if (!remote || get_sha1(remote, rev))
 857                                 return argcount;
 858                         *new_branch = arg;
 859                         arg = remote;
 860                         /* DWIMmed to create local branch */
 861                 } else {
 862                         return argcount;
 863                 }
 864         }
 865
 866         /* we can't end up being in (2) anymore, eat the argument */
 867         argcount++;
 868         argv++;
 869         argc--;
 870
 871         new->name = arg;
 872         setup_branch_path(new);
 873
 874         if (!check_refname_format(new->path, 0) &&
 875             resolve_ref(new->path, branch_rev, 1, NULL))
 876                 hashcpy(rev, branch_rev);
 877         else
 878                 new->path = NULL; /* not an existing branch */
 879
 880         new->commit = lookup_commit_reference_gently(rev, 1);
 881         if (!new->commit) {
 882                 /* not a commit */
 883                 *source_tree = parse_tree_indirect(rev);
 884         } else {
 885                 parse_commit(new->commit);
 886                 *source_tree = new->commit->tree;
 887         }
 888
 889         if (!*source_tree)                   /* case (1): want a tree */
 890                 die(_("reference is not a tree: %s"), arg);
 891         if (!has_dash_dash) {/* case (3 -> 1) */
 892                 /*
 893                  * Do not complain the most common case
 894                  *      git checkout branch
 895                  * even if there happen to be a file called 'branch';
 896                  * it would be extremely annoying.
 897                  */
 898                 if (argc)
 899                         verify_non_filename(NULL, arg);
 900         } else {
 901                 argcount++;
 902                 argv++;
 903                 argc--;
 904         }
 905
 906         return argcount;
 907 }
 908
 909 int cmd_checkout(int argc, const char **argv, const char *prefix)
 910 {
 911         struct checkout_opts opts;
 912         unsigned char rev[20];
 913         struct branch_info new;
 914         struct tree *source_tree = NULL;
 915         char *conflict_style = NULL;
 916         int patch_mode = 0;
 917         int dwim_new_local_branch = 1;
 918         struct option options[] = {
 919                 OPT__QUIET(&opts.quiet, "suppress progress reporting"),
 920                 OPT_STRING('b', NULL, &opts.new_branch, "branch",
 921                            "create and checkout a new branch"),
 922                 OPT_STRING('B', NULL, &opts.new_branch_force, "branch",
 923                            "create/reset and checkout a branch"),
 924                 OPT_BOOLEAN('l', NULL, &opts.new_branch_log, "create reflog for new branch"),
 925                 OPT_BOOLEAN(0, "detach", &opts.force_detach, "detach the HEAD at named commit"),
 926                 OPT_SET_INT('t', "track",  &opts.track, "set upstream info for new branch",
 927                         BRANCH_TRACK_EXPLICIT),
 928                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, "new branch", "new unparented branch"),
 929                 OPT_SET_INT('2', "ours", &opts.writeout_stage, "checkout our version for unmerged files",
 930                             2),
 931                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, "checkout their version for unmerged files",
 932                             3),
 933                 OPT__FORCE(&opts.force, "force checkout (throw away local modifications)"),
 934                 OPT_BOOLEAN('m', "merge", &opts.merge, "perform a 3-way merge with the new branch"),
 935                 OPT_STRING(0, "conflict", &conflict_style, "style",
 936                            "conflict style (merge or diff3)"),
 937                 OPT_BOOLEAN('p', "patch", &patch_mode, "select hunks interactively"),
 938                 { OPTION_BOOLEAN, 0, "guess", &dwim_new_local_branch, NULL,
 939                   "second guess 'git checkout no-such-branch'",
 940                   PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
 941                 OPT_END(),
 942         };
 943
 944         memset(&opts, 0, sizeof(opts));
 945         memset(&new, 0, sizeof(new));
 946
 947         gitmodules_config();
 948         git_config(git_checkout_config, &opts);
 949
 950         opts.track = BRANCH_TRACK_UNSPECIFIED;
 951
 952         argc = parse_options(argc, argv, prefix, options, checkout_usage,
 953                              PARSE_OPT_KEEP_DASHDASH);
 954
 955         /* we can assume from now on new_branch = !new_branch_force */
 956         if (opts.new_branch && opts.new_branch_force)
 957                 die(_("-B cannot be used with -b"));
 958
 959         /* copy -B over to -b, so that we can just check the latter */
 960         if (opts.new_branch_force)
 961                 opts.new_branch = opts.new_branch_force;
 962
 963         if (patch_mode && (opts.track > 0 || opts.new_branch
 964                            || opts.new_branch_log || opts.merge || opts.force
 965                            || opts.force_detach))
 966                 die (_("--patch is incompatible with all other options"));
 967
 968         if (opts.force_detach && (opts.new_branch || opts.new_orphan_branch))
 969                 die(_("--detach cannot be used with -b/-B/--orphan"));
 970         if (opts.force_detach && 0 < opts.track)
 971                 die(_("--detach cannot be used with -t"));
 972
 973         /* --track without -b should DWIM */
 974         if (0 < opts.track && !opts.new_branch) {
 975                 const char *argv0 = argv[0];
 976                 if (!argc || !strcmp(argv0, "--"))
 977                         die (_("--track needs a branch name"));
 978                 if (!prefixcmp(argv0, "refs/"))
 979                         argv0 += 5;
 980                 if (!prefixcmp(argv0, "remotes/"))
 981                         argv0 += 8;
 982                 argv0 = strchr(argv0, '/');
 983                 if (!argv0 || !argv0[1])
 984                         die (_("Missing branch name; try -b"));
 985                 opts.new_branch = argv0 + 1;
 986         }
 987
 988         if (opts.new_orphan_branch) {
 989                 if (opts.new_branch)
 990                         die(_("--orphan and -b|-B are mutually exclusive"));
 991                 if (opts.track > 0)
 992                         die(_("--orphan cannot be used with -t"));
 993                 opts.new_branch = opts.new_orphan_branch;
 994         }
 995
 996         if (conflict_style) {
 997                 opts.merge = 1; /* implied */
 998                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
 999         }
1000
1001         if (opts.force && opts.merge)
1002                 die(_("git checkout: -f and -m are incompatible"));
1003
1004         /*
1005          * Extract branch name from command line arguments, so
1006          * all that is left is pathspecs.
1007          *
1008          * Handle
1009          *
1010          *  1) git checkout <tree> -- [<paths>]
1011          *  2) git checkout -- [<paths>]
1012          *  3) git checkout <something> [<paths>]
1013          *
1014          * including "last branch" syntax and DWIM-ery for names of
1015          * remote branches, erroring out for invalid or ambiguous cases.
1016          */
1017         if (argc) {
1018                 int dwim_ok =
1019                         !patch_mode &&
1020                         dwim_new_local_branch &&
1021                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1022                         !opts.new_branch;
1023                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1024                                 &new, &source_tree, rev, &opts.new_branch);
1025                 argv += n;
1026                 argc -= n;
1027         }
1028
1029         if (opts.track == BRANCH_TRACK_UNSPECIFIED)
1030                 opts.track = git_branch_track;
1031
1032         if (argc) {
1033                 const char **pathspec = get_pathspec(prefix, argv);
1034
1035                 if (!pathspec)
1036                         die(_("invalid path specification"));
1037
1038                 if (patch_mode)
1039                         return interactive_checkout(new.name, pathspec, &opts);
1040
1041                 /* Checkout paths */
1042                 if (opts.new_branch) {
1043                         if (argc == 1) {
1044                                 die(_("git checkout: updating paths is incompatible with switching branches.\nDid you intend to checkout '%s' which can not be resolved as commit?"), argv[0]);
1045                         } else {
1046                                 die(_("git checkout: updating paths is incompatible with switching branches."));
1047                         }
1048                 }
1049
1050                 if (opts.force_detach)
1051                         die(_("git checkout: --detach does not take a path argument"));
1052
1053                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1054                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\nchecking out of the index."));
1055
1056                 return checkout_paths(source_tree, pathspec, prefix, &opts);
1057         }
1058
1059         if (patch_mode)
1060                 return interactive_checkout(new.name, NULL, &opts);
1061
1062         if (opts.new_branch) {
1063                 struct strbuf buf = STRBUF_INIT;
1064
1065                 opts.branch_exists = validate_new_branchname(opts.new_branch, &buf,
1066                                                              !!opts.new_branch_force, 0);
1067
1068                 strbuf_release(&buf);
1069         }
1070
1071         if (new.name && !new.commit) {
1072                 die(_("Cannot switch branch to a non-commit."));
1073         }
1074         if (opts.writeout_stage)
1075                 die(_("--ours/--theirs is incompatible with switching branches."));
1076
1077         return switch_branches(&opts, &new);
1078 }